Extruded pet parison, container, and method

ABSTRACT

An extruded PET parison includes a first extruded polymer comprising PET, and a second extruded polymer comprising PET. In embodiments, the first extruded polymer and the second extruded polymer are co-extruded, and the first extruded polymer has an intrinsic viscosity that is higher that the intrinsic viscosity of the second extruded polymer. A monolayer embodiment is also disclosed. In embodiments, a monolayer extruded PET container is comprised of bottle grade PET resin that has been solid stated and may have an IV from about 0.96 to about 1.4.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/595,802, filed Aug. 27, 2012, now pending. U.S. Ser. No. 13/595,802claims the benefit of priority to US Provisional Application No.61/527,443, filed Aug. 25, 2011 and U.S. Provisional Application61/590,652, filed Jan. 25, 2012, the entire disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to extrusion blow molding (EBM)methods and systems capable of utilizing injection stretch blow molding(ISBM) grade polyethylene terephthalate (PET) to produce articlesincluding bottles and containers.

BACKGROUND

Polymer resins, including PET, are commonly employed in the plasticpackaging industry. Because of its favorable processing properties, andbecause PET is considered recycling-friendly, PET is widely used toproduce numerous types of bottles and containers (which may herein becollectively referred to as simply “containers”). In the bottleindustry, for example, bottle-grade PET usually has a resin intrinsicviscosity (IV) of about 0.65 to 0.87 dL/g, and is commonly used inconnection with ISBM processing.

Extrudable PET compositions or formulations (e.g., extrudable PETco-polymers) are also known in the packaging industry. EBM PET can bedesirable in connection with a number of applications, as it can permitthe use of PET to form articles that are commonly formed from HDPE, forexample, large plastic containers with handles. For PET to be suitablefor EBM processes, a higher molecular weight PET, i.e., one having ahigher IV (e.g., about 1.0 dL/g or greater) may be needed. However, suchco-polymers are commonly amorphous, or slow-crystallizing, which canpresent certain conversion and reclamation challenges. While aslow-crystallizing co-polymer may allow for easier processing in EBMenvironments, the resulting container can, among other things, presentrecyclability challenges. For instance, when the material has not yetcrystallized, and remains amorphous, it may melt at lower temperatures.Further, when amorphous or slow crystallizing resins are added to thePET recycling stream, the resins can cause, inter alia, unwantedsticking, thermal agglomeration, and bridging (or port plugging) issues.Such issues can make PET polymer resins unsuitable for conventionalrecycling programs and processes. Containers using Eastman EBO62material fall into this category as can they present such recycling andperformance issues since the PET resin is modified with additives forincreased melt strength.

Moreover, if a bottle grade PET and an extrudable PET composition areblended or combined, so as to be provided in the form of branched PETcopolymers, the resulting combination of resins may not exhibitperformance characteristics that are sufficiently desirable. That isgenerally from a recycling standpoint, the higher percentage ofextrusion-grade PET, the more undesirable the characteristics of theresulting product.

The use of standard ISBM-grade PET in the extrusion context might helpto address some the aforementioned recyclability issues. However, forreasons such as noted above, such resins have generally not beensuccessfully commercialized because of a number of challenges. Suchresins typically have a low IV, i.e., commonly from about 0.65 to 0.87.As a result, they tend not to be able to carry their own weight and/orthe resins may extrude too quickly to form a desired capturable parison.This presents a problem for most, if not all, EBM processes, whichrequires adequate melt strength in order to produce an acceptableparison (whether it be in a shuttle EBM system, a wheel EBM system, orany other). Without adequate melt strength, the parison will not formcorrectly and may flow too quickly (“like water”) to be captured by ablow mold. Additionally, with some articles, a lower IV may provide lesscontainer strength, more susceptibility to stress fractures or cracks,and undesirable visual haze or streaks.

Consequently, there remains a desire for an EBM method and system toproduce commercially acceptable and bottles and/or containers that arecompatible with the recycling stream from extrusion-grade PETcompositions or formulations.

SUMMARY

Extruded PET parisons, containers, and methods of producing suchparisons and containers are disclosed. In embodiments, a first extrudedpolymer and a second extruded polymer are co-extruded, the firstextruded polymer comprises PET, the second extruded polymer comprisesPET, and the intrinsic viscosity of the first extruded polymer is higherthat the intrinsic viscosity of the second extruded polymer. Theco-extruded parison may be subsequently blow molded to form a container.

In the as embodiment, the first extruded polymer (i.e., the higher IVpolymer) may comprise PET having an IV of from about 0.96 or greater. Ifdesired, the first extruded polymer may have an IV from about 1.0 to1.4, and may, for example, be created by solid-stating standard bottlegrade PET and may be devoid of chain extenders. The second extrudedpolymer (i.e., the lower IV polymer) may also comprise PET, and may havean IV of about 0.85 or less. If desired, the second extruded polymer mayhave an IV of from about 0.8 to 0.85. Additionally, the second extrudedpolymer may further comprise post-consumer recycled (PCR) PET andregrind PET, and/or may optionally include a colorant and/or a barrier.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, wherein:

FIG. 1 is a partially broken away view that generally illustrates anembodiment of a multi-layer extrusion blow molded container;

FIG. 2 is a partial sectional view that generally illustrates a wall ofthe molded container;

FIG. 3 is a partial sectional view of a wall of an embodiment of anintermediate article; and

FIG. 4 is a partial sectional view of a wall of another embodiment,which is associated with a monolayer article.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are described herein and illustrated in theaccompanying drawings. While the invention will be described inconjunction with embodiments, it will be understood that they are notintended to limit the invention to these embodiments. On the contrary,the invention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims.

By way of example only, and without limitation, FIG. 1 generally shows apartially broken away view that generally illustrates an embodiment of amulti-layer extrusion-blow molded container 10. FIG. 2 depicts a partialsectional view that generally illustrates a portion of a wall(identified as portion A) of the container 10. In the illustratedembodiment, innermost three layers 12, 14, 16 may be formed in a firstprocessing stage—which may involve co-extrusion or multiple extrusionsof materials—and may provide an intermediate article 20. In theillustrated embodiment an optional, fourth/outermost layer 18 isincluded. The optional outermost layer, if included, 18 may be comprisedof similar or different plastic material than the other layers and, ifdesired, may comprise a coating. An embodiment of a wall portion of anintermediate article is generally illustrated in FIG. 3. While threelayers are disclosed in connection with the intermediate article 20, andfour layers are disclosed in connection with the container 10, those ofskill in the art will recognize that more layers (or even less layerswith respect to the intermediate article 20) may be provided and thelayers may have different configurations and thicknesses (includingdiffering thicknesses as to a given layer and relative layer-to-layerthickness variations). FIG. 4 generally illustrates an embodiment of awall portion of a monolayer article or container. The article orcontainer is generally comprised of a single layer (generallyillustrated as layer 14).

In embodiments of the present disclosure, a method is provided in whichtwo or more polymers are co-extruded to form a parison that can besubsequently blow into a bottle or container. In an embodiment, twoseparate polymers may be provided. A first polymer may comprise PET andmay have a comparatively higher IV—e.g., 0.96 or greater (or, forinstance, from about 1.0 to about 1.4). The first polymer may, forexample and without limitation, be created by solid-stating standardbottle grade PET and may be devoid of chain extenders. A second polymermay also comprise PET and may have a comparatively lower IV—forinstance, less than about 0.85 (or, for example, from about 0.8 to about0.87). The second polymer, i.e., having a comparatively lower IV, maycomprise post-consumer recycled (PCR) PET and/or regrind PET. Moreover,for some embodiments, the second polymer may additionally include one ormore colorants.

In an embodiment, the first polymer may be provided with an IV of, forexample, about 0.97, while a second polymer may have an IV of, forexample, 0.76. The layer with the comparatively higher IV can serve tohandle higher melt temperatures and provide strength, and canadditionally help to prevent migration.

In embodiments of a method and system, the first (higher IV) and second(lower IV) polymers may be extruded and combined—e.g., via an extrusionhead—to form a parison having multiple (e.g., two) layers. In anembodiment, the cross-sectional thickness (along the sidewall andperpendicular to the centerline of the parison) of the higher-IV layermay be about 20% (0.20) of the total parison thickness, and thethickness of the lower-IV layer may be about 80% (0.80) of the totalparison thickness. Further, depending on the desired content of theresulting bottle or container, the higher-IV layer and the lower-IVlayer may be interchanged with respect to which layer is the innerco-extruded layer and which layer is the outer co-extruded layer.

Embodiments of bottles and containers produced in accordance with thepresent disclosure may comprise crystalline PET, may exhibitcommercially acceptable clarity, and may be fully recyclable in thestandard PET recycling stream (i.e., marked as “No. 1”).

In embodiments, an extrudable PET—that is not solid-stated—may have a“composite” IV of about 0.96, or less, so as to be able to extrude down.The invention is not, however, limited to equipment that extrudes in thedirection of gravity, and other known techniques may be employed.

Further, the disclosed method and system may be applied to parisonsformed in one co-extruded layer, or in multi-layer embodiments that havetwo or more extruded layers. Moreover, in embodiments, one layer mayserve as a carrier layer, while the other layer(s) may impart one ormore other structures or features. Such other structures or features mayinclude the use of PCR, coloring (e.g., an outside color), or costoptimization (e.g., inclusion of a comparatively less expensive (“junk”)middle layer). Without limitation, in an embodiment the a comparativelyhigh-IV polymer may serve as a skeleton, while another layer may includeas much as 28% or more PCR. Further, without limitation, someembodiments of resulting bottles or containers may comprise a PCRcontent of between about 10% to 50% by weight. In other embodiments, thePCR content may be in the nature of about 20% to 30% by weight.Moreover, if desired, a junk layer of 80% or more (even up to 100%) PCRmay additionally be included. Embodiments of the present disclosure arenot dependent upon chain extenders, and are not combinations ofamorphous and solid state resins. That is, the extrudable polymers canbe provided in a solid state condition, and are not amorphous.

A potential benefit of a dual layer is the ability to utilize a carrierresin. It is also possible to color one or both layers to providedifferent visual effects, whether the layer or layers are colored aloneor in various combinations. Further, if permeation is a potential issue,one or more barrier layers may be employed in connection with one ormore layers of the parison/article.

Parisons associated with the disclosed concept may be processedutilizing various forms of known processing techniques and equipment.For some embodiments, a “shuttle”-type system may be used. Withshuttle-type equipment a head with multiple outlets may provide aparison at a common spot and a mold or molds can be moved, or shuttled,in position under the parison. Such a system may work well if space isan issue and/or if production will be more “on demand” with lessconcerns about high capacity and speed. Alternatively, various knownrotary or “wheel” extrusion techniques may be employed where a more“continuous” process, with potentially higher speed and output, isdesirable. In embodiments, wheel extrusion devices and apparatus may, asdesired, be configured to extrude in various directions—for example,upwards or, perhaps more desirably for some applications, downwards.

Another embodiment of the present disclosure comprises a monolayerextruded PET container made from standard bottle grade PET resin thathas been solid-stated. Standard bottle grade PET resin may have an IV offrom about 0.65 to about 0.87. With embodiments of the instantdisclosure, such PET resin may be solid-stated to increase its IV tofrom about 0.96 to about 1.4, and for some embodiments, about 1.1. Suchresin may be devoid of chain extenders or other similar additives ormodifiers. Extrusion blow molding of such resin, for example inconnection with a downward-extruding wheel process, can produce arecyclable (e.g., #1 marked) PET container with good clarity andmaterial distribution (which can result in improved container strengthand performance). As referenced herein “good clarity” may describecontainers that are substantially free of striations and/or haze.Containers produced in accordance with the teachings of this disclosurecan result in containers that are well suited to withstand drop tests,including conventional three-foot drop tests (which may be “chilled” or“unchilled” tests). That is, with limited testing, a significant number(e.g., greater that 50%) of the tested containers pass a three-foot droptest. In embodiments, in connection with the EBM processing of suchresin, it can be desirable to maintain generally consistent moldtemperatures.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and various modifications andvariations are possible in light of the above teaching. The embodimentswere chosen and described in order to explain the principles of theinvention and its practical application, to thereby enable othersskilled in the art to utilize the invention and various embodiments withvarious modifications as are suited to the particular use contemplated.It is intended that the scope of the invention be defined by the claimsappended hereto and their equivalents.

What is claimed is:
 1. An extruded PET parison comprising: a firstextruded polymer comprising PET; and a second extruded polymercomprising PET; wherein the first and second polymers are co-extruded,the first and second extruded polymers are in a solid state, and thefirst extruded polymer has an intrinsic viscosity that is higher thatthe intrinsic viscosity of the second extruded polymer.
 2. The parisonof claim 1, wherein the first extruded polymer has an intrinsicviscosity of at least 0.96.
 3. The parison of claim 1, wherein the firstextruded polymer has an intrinsic viscosity from about 1.0 to about 1.4.4. The parison of claim 1, wherein the second extruded polymer has anintrinsic viscosity of less than 0.85.
 5. The parison of claim 1,wherein the second extruded polymer has an intrinsic viscosity of about0.80 to about 0.87.
 6. The parison of claim 1, wherein the secondextruded polymer comprises post-consumer recycled (PCR) PET or regrindPET.
 7. The parison of claim 1, wherein the second extruded polymerincludes a colorant.
 8. The parison of claim 1, wherein thecross-sectional thickness of the first extruded polymer is at leastabout 0.20 of the total parison thickness.
 9. The parison of claim 1,wherein the cross-sectional thickness of the second extruded polymer isless than about 0.80 of the total parison thickness.
 10. The parison ofclaim 1, including one or more additional extruded polymer layers. 11.The parison of claim 10, wherein the one or more additional extrudedpolymer layers comprise recycled or reground material.
 12. A containerformed from the parison of claim
 1. 13. An extruded PET parisoncomprising: an extruded monolayer polymer comprising PET; wherein theextruded monolayer polymer is in a solid state, and the extrudedmonolayer polymer has an intrinsic viscosity from about 0.96 to about1.4 and is devoid of chain extenders.
 14. The parison of claim 13,wherein the intrinsic viscosity is about 1.1.
 15. A container formedfrom the parison of claim
 13. 16. The container of claim 15, wherein thecontainer is substantially free of striations and haze.